Combine buttermilk and Grape-Nuts in a bowl. Allow to soak for 10 minutes. Preheat oven to 350 F.,______,Sift flour, salt, baking soda and baking powder together in a smaller bowl then stir thoroughly into the Grape-Nuts mixture.,Pour into 2 greased and floured standard size loaf pans. Bake at 350 F for 45 minutes or until a toothpick inserted in the center comes out clean. Remove from oven. Cool and serve!